• d-bugmail puremagic.com (38/43) May 18 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6035
• d-bugmail puremagic.com (6/6) May 18 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6035
• d-bugmail puremagic.com (10/10) May 18 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6035
• d-bugmail puremagic.com (12/13) May 19 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6035

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6035

           Summary: std.algorithm.reversed()
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



std.algorithm has a reverse() function:
http://www.digitalmars.com/d/2.0/phobos/std_algorithm.html#reverse

(reverse() returns void, this is correct and right, because it works in-place.
Returning the reversed array is the wrong thing to do.)

reverse duplicates what the array reverse attribute performs:

auto a = [1, 2, 3];
a.reverse;


But in functional-style code I want to create expressions, so I can't use a
function (a procedure) that returns void:

foreach (x; reversed(foo(array1))) {...


And sometimes I don't to work-in place, I need a reversed view of something
that I don't want to modify. So I suggest to introduce a
std.algorithm.reversed() (or std.range.reversed()) function, that lazily yieds
the reversed items, as in Python:

 a



['a', 'b', 'c', 'd']
 a = [1, 2, 3]
 reversed(a)



<listreverseiterator object at 0x01A02910>
 list(reversed(a))



[3, 2, 1]
 a



[1, 2, 3]


Returning a copy is also useful for immutable arrays, and generally it fits
better in functional-style programming.

See also enhancement issue 5076 that's about sorted(), another function usable
in expressions, that doesn't modify the original iterable.

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6035




For an usage example see issue 6034

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6035


kennytm gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kennytm gmail.com



std.range.retro ?

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6035


bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID




 std.range.retro ?

Sorry for the noise.

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